After Vista SP1, the worst that will happen is a warning notice that forces a 15-second delay at login, and a reminder every hour on the hour to activate.
Gates famously stated in the past that if people pirated an OS he would prefer it to be Windows. Microsoft forgot this for a while, but there is a glimmer of a re awakening. Don't be fooled by the bad product that is Vista. There is a long way to go before Microsoft runs out of money!